Ampro 486E P/N 5001561 Revision A, Manual

Page: 39 / 118

Product Reference
2–23
;----------------------------------------------------------
; Code to change the parallel port direction to input
;----------------------------------------------------------
MOV DX,37Ah
IN AL,DX
OR AL,20h ;set bit 5
OUT DX,AL
;
;----------------------------------------------------------
; Code to change the parallel port direction to output
;----------------------------------------------------------
MOV DX,37Ah
IN AL,DX
AND AL,0DFh ;clear bit 5
OUT DX,AL
Parallel Port Interrupt
The parallel port can be configured to generate an interrupt request upon a variety of conditions. In
most applications, the interrupt is not used. The standard parallel port interrupts are IRQ7 for the
primary port and IRQ5 for the secondary port. The IRQ channel assignments are standard and
cannot be changed. A bit in the parallel port's command registers enables or disables the port’s
connection to its interrupt line.